The invention relates to an automated inspection apparatus and method for use in the optical inspection of 3-dimensional (3D) translucent objects such as fish, to simultaneously identify surface, embedded and semi-transparent edge anomalies and distinguishing features.
Translucent objects, such as fish, often contain defects or conditions which lead to or cause contamination of the object. It is necessary to eliminate these, contaminated areas or objects and, as such, a reliable method for detecting these features or anomalies has been the subject matter of certain prior art.
Reliable detection of optical characteristics of a translucent object poses difficulties due to illumination, which is used during inspection, being either adsorbed by the object or scattered unevenly over the object. Conventional illumination can be too bright in certain areas or too dim in others. Another problem associated with detection of foreign objects is the creation of shadows or extreme brightness which results in an image capture device xe2x80x9cstopping-upxe2x80x9d or xe2x80x9cstopping-downxe2x80x9d the aperture to prevent under or overexposure.
Typical light sources range from conventional light fixtures to ultra violet spectrum. As an example, halogen lighting can be used to provide an overall light source for the inspection of an object such as a fish fillet. The use of UV is standard for the purposes of inspecting glass.
Surface, embedded and semi-transparent edge anomalies in translucent objects such as fish are characteristically only manifested under appropriate dark field or bright field illumination. As such, dark and bright field illumination are typically addressed individually due to light path propagation during compensation for individual manifestation characteristics of the anomalies.
For example, bright field lighting is a lighting technique which directs specular or diffuse reflections of light to the camera. Surface defects, such as blood and skin are detected with this technique. Dark field lighting is a lighting technique which directs back scattered light from the surface of an object to the camera. Embedded, anomalies, such as a parasite, and semi-transparent edge anomalies, such as transparent bones, in a fish fillet are detectable. with this technique. However, use of either technique presents known difficulties as summarized hereinafter. Changing light levels or the creation of geometrical shadows can distort accurate sensor detection.
Conventional methods used for anomaly detection for fish processing entail placing a fish on a light table having a surface illuminated. At least one lamp is used to illuminate the target area in bright field light. Operators visibly inspect a fish fillet to identify surface, embedded and semi-transparent edge anomalies.
Inherent to this method is visual fatigue, inconsistent visual perception by an operator and optical disparity between operators. Attempts have been made to overcome these difficulties by known art.
Examples of art that discuss several ways of properly illuminating and inspecting an object. include U.S. Pat. Nos. 4,585,315; 5,845,002; 6,022,124; 6,049,379; 5,493,123; international patents PCT/US95/11318 (equivalent to U.S. Pat. No. ""002); PCT/US97/20058; Japanese patents 3165534A2; 8201222A2; and 11108637A2.
U.S. Pat. No. ""315 discusses a bright field and dark field microscope illuminator with two axicon mirrors, a third plane mirror and shutters positioned in the paths of the light beams. Through use of the disclosed embodiments, simultaneous bright and dark field illumination or alternatively singularly bright or dark field illumination is achieved through the opening and closing of the appropriate shutters. However, the advantages of even illumination of a translucent object would technically obviate from detection of translucent or transparent anomalies that would manifest under variant light intensities. Simultaneous detection of surface, embedded and semitransparent edge anomalies is not possible with the use of only dark or bright field illumination.
U.S. Pat. No. ""002 teaches a method of statistical evaluation of a translucent object by scanning graphic images of an object and processing incident light frequencies enabling a pixel by pixel analysis of topographic surface features of a fruit. A selected frequency, or combinations of frequencies, of light is directed at the fruit according to porosity of the peel. A computerized optical scanner having two light sources disposed at approximately 120 degrees from a vertical plane emit incident light towards an object, or to mirrors, to effectively scatter incident light within the fruit and cause the fruit to xe2x80x9cglowxe2x80x9d. A frequency spectrum is selected based on maximum, minimum and standard deviation of the intensity of the entire pixel pattern constituting the image. Both hemispheres of a fruit are analyzed; an algorithm assists in eliminating portions of the graphic information that are not relevant (such as bright field illumination or reflected light sources), and which do not constitute xe2x80x9cglowxe2x80x9d from the fruit. Sharp transitions are evaluated by filtering the image and comparing aberrations pixel by pixel. International application WO 96/14169 is derived from U.S. Pat. No. ""002. Application of the above methodology prohibits bright field illumination techniques that enable detection of transparent anomalies such as skin and bones embedded or on the surface of a fish fillet.
U.S. Pat. No. ""124 discloses a ring-light source and reflective ring focusing element wherein LED""s are strung in one or more circular rows and strobe (or pulse) light to ring reflectors provides uniform lighting of an object. Light emissions from the LED""s approach the object at an angle oblique or perpendicular to the optical axis. The effective dark field illumination patterns are intended to minimize light from the illumination source from entering the camera. However, use of only a dark field technique during inspection of a translucent object, such as a fish, severely diminishes the manifestation of those anomalies, thus requiring bright field techniques.
U.S. Pat. No. ""379 shows a method of scanning multiple images of a translucent object and applying brightness ratios to the scanned images for the detection of flaws in the target area. A glass bottle is disclosed wherein light intensity readings are analyzed based on an acceptable range of ratios determined by a target area and a control area. The allowable range is calculated by analyzing an object with known defects and an object that is known-to be non-defective. The disclosure notes that xe2x80x9cblind spotsxe2x80x9d may arise during inspection for defects.
The techniques of U.S. Pat. No. ""123 involves the use of ultra violet radiation during a predetermined inspection period of glass. Use of ultra violet radiation during the inspection of organic materials for consumption is not desirable.
International patent PCT/US97/20058 discloses an automated inspection system with bright field and dark field illumination. The detection of xe2x80x9cmacro-defectsxe2x80x9d such as scratches, incomplete photoresist coverage and non-uniform edge bead removal on a semiconductor wafer are detectable through the use of simultaneous bright and dark field illumination. Image data acquisition is achieved through illumination of an object by at least two light sources wherein light striking the patterned surface of a wafer respectively propagates dark and light field light paths which are collected by an imaging lens. Light sensitive sensors are positioned behind the lenses which concentrate the light passing through them on the light receiving surfaces of the sensors. Data captured by the light sensors is output in a form of digital data streams. The streams of digital data are processed for creation of a gray level deviation map from which an absolute difference image is used to detect bright field and dark field, defects. Although the above addresses nanometer topographical defects, subtleties of light degradation impede detection of transparent anomalies such as bones and parasites in translucent objects. Fish is not described for use in the method.
Japanese patent ""534 A2 shows a device for inspecting defects. A binary image is formed using a light-field comparator by the instruction of the controller. Bright field illumination is removed and the roughed part of the object is inspected using only dark field illumination. Dark field illumination is removed and the plane part of an object is inspected using only light field illumination. This Japanese patent does not disclose a method of simultaneous detection of anomalies.
Japanese patent ""222 A2 discusses a method for inspecting lenticular lens sheet.
The inspection apparatus reflects only dark field illumination to comprise the image using a xe2x80x9cpickup means ofxe2x80x9d CCD line sensor cameras. Use of only dark field illumination impedes detection of anomalies only detectable by use of bright field illumination techniques.
Finally, an inspection device is disclosed in Japanese patent ""637 A2. Use of a bright field lighting source or a dark field lighting source is selected according to the object being inspected, optionally both may be used.
The above references are known to improve the overall detection of distinguishing features and anomalies in objects, but none of the above art provides a solution for simultaneous detection of surface, embedded and semi-transparent edge anomalies.
The purpose of the invention is therefore to provide an automatic inspection apparatus and method for simultaneous detection of surface, embedded and semi-transparent edge anomalies in translucent objects.
It is therefore a feature of certain embodiments of the present invention to provide an automated imaging apparatus for detection of anomalies in 3D translucent objects.
In one embodiment, there is provided an automated inspection apparatus detection of anomalies in a 3D translucent object, the apparatus having a scanhead assembly including an image processing unit and image capture device, a first and a second light source, and conveyor means, a light block member positioned along a substantially common axis of the image capture device and a light source.
A further aspect of the present invention of the above embodiment is where the scanhead assembly has an image capture device, a computer processing unit in use with the image capture device to store and/or output scanned images and the assembly also includes an illumination member having illumination means which operates to illuminate the object being inspected as well as support means for moving an object in the desired direction and the light block member includes a signal isolation means.
In another preferred aspect of the above embodiment of the present invention the apparatus has the first and second light sources being comprised of bright and dark field, respectively, the conveyer is made of a translucent material having diffusion properties, the light block member is made of a material having selective light transfer properties, and the signal isolation means is video paint which can be positioned therein or thereon.
A particularly preferred aspect of the scanhead assembly is where it includes at least one reflection member and the object displacement for isolating the objects having anomalies includes the use of pneumatic ejector arms.
In another embodiment of a preferred aspect of the invention, there is provided a frame assembly, having object displacement means, a conveyor means, a scanhead assembly, and further includes a light block member, and a first and a second illumination member, whereby the light block member being positioned between an illumination member and the translucent object. The frame assembly mounts the scanhead assembly. Those skilled in the art will understand the varying positioning of the assembly (separate, or otherwise), the illumination members and the light block member are in a spaced apart relationship whereby the scanhead assembly, the light source and the light block member are positioned along a substantially common axis.
It is also an aspect of the above embodiment that the scanhead assembly has an illumination member, an image storage device, a computer processing unit, an image capture device and at least one mirror, whereby the image capture device is adapted to be used with the computer processing unit; the image capture device, the light member and the translucent object are positioned coaxially.
A further aspect of the above embodiment is where the apparatus includes the first and second light sources being comprised of bright and dark field, respectively, the conveyer is made of a translucent material having diffusion properties, the light block member is made of a material having selective light transfer properties, and the signal isolation means includes video paint which can be positioned therein or thereon, the isolation means for isolating objects with anomalies includes pneumatic ejector arms.
According to another aspect of the present invention, there is provided a method of simultaneously detecting surface, embedded and semi-transparent edge anomalies in 3D translucent objects, includes the steps of:
providing a translucent object;
providing an image capture means for recording or viewing scanned image of translucent object;
illuminating an object with spaced apart first and second illumination members together with light diffusion member;
providing a light block member positioned between the second illumination means and the translucent object;
aligning an image capture device, a light block member and a second illumination member along a substantially common axis; and,
scanning a translucent object for anomalies with an image capture device to acquire data images for simultaneous detection of anomalies.
In preferred embodiments of the above invention, there is included the step of providing the images to an image processing unit for the detection of anomalies present on or within a translucent object. In a further desirable embodiment scanning a translucent object may be achieved while an object moves between the illumination members and an image capture device. Preferably, a translucent object is an edible foodstuff. Furthermore, it is desirable the above embodiment includes use during food manufacture.
The present invention will also find use in other fields for detecting anomalies. An example of additional fields would be meat processing, such as chicken, as well as other edible foods stuffs, such as fruits and legumes. Further fields for the invention may be used includes glass, plastics, foam and the like where defects and anomalies are to be detected.
A 3D translucent object, at least a portion of whose surface region is translucent or absorbs light is, for the purposes of the description used in the specification, is to be considered to be a translucent object, since some absorption or reflection would occur in such an object and would permit application of the methods and apparatus of this. invention. An example of such an object would be a fish fillet wherein light would be absorbed by embedded and semi-transparent edge anomalies (which may also reflect light) and reflected by surface anomalies. Such imperfections would allow for the detection of these anomalies according to this invention.
Reference to objects herein can therefore be understood to include any object falling within the foregoing, including but not limited to a fish fillet. Likewise, reference to fish or particular nomenclature thereof can be understood to refer to any object which might be sorted according to the method and apparatus of this invention.